Systems and methods for joining a first structure and a second structure with a choreographed adhesive de-aeration process

ABSTRACT

An example method of joining a first structure and a second structure is described that includes placing an adhesive within a bond cavity for bonding a first structure to a second structure, securing a vacuum bag to the first structure and the second structure so as to surround a portion of the first structure and the second structure, evacuating the bond cavity via a vacuum port to deaerate the adhesive within the bond cavity, after deaerating the adhesive, moving the first structure and the second structure relative to one another such that deaerated adhesive is disposed between the first structure and the second structure, and curing, via one or more heaters, the deaerated adhesive disposed between the first structure and the second structure to bond the first structure to the second structure.

CROSS REFERENCE TO RELATED APPLICATION

The present disclosure is a divisional of and claims priority to U.S.application Ser. No. 17/502,270, filed on Oct. 15, 2021, which claimspriority to U.S. Provisional Application No. 63/126,626, filed on Dec.17, 2020, the entire contents of each of which are herein incorporatedby reference.

FIELD

The present disclosure relates generally to forming a bonded structure.In particular, the present disclosure relates to reducing voids inbondlines between a first structure and a second structure and forming avoid free bondline.

BACKGROUND

Components used in vehicles, such as wings used in aircraft, includeseveral bonded members. For example, exterior surfaces of a wing, andthe structures used to provide support for those surfaces, may beconstructed in a bonded manner using adhesives to create bondelines.

Currently, bonds for large or complex structures involve resin transfermolding, high tolerance film adhesive, or costly co-cure methods.Further, currently, paste bonds such as those that may be used in pijoints and single shear joints in aircraft, utilize adhesive injectionapproaches that can create bondlines between the bonded members thathave some voids and variation in strength, and accordingly, may be ratedwith a lower performance capability.

As such, there is a desire for an improved bonding method to producehigher quality bonds in a low cost manner.

SUMMARY

In an example, a method of joining a first structure and a secondstructure is described. The method comprises placing an adhesive withina bond cavity for bonding a first structure to a second structure,securing a vacuum bag to the first structure and the second structure soas to surround a portion of the first structure and the secondstructure, evacuating the bond cavity via a vacuum port to deaerate theadhesive within the bond cavity, after deaerating the adhesive, movingthe first structure and the second structure relative to one anothersuch that deaerated adhesive is disposed between the first structure andthe second structure, and curing, via one or more heaters, the deaeratedadhesive disposed between the first structure and the second structureto bond the first structure to the second structure.

In another example, a bondline joining a first structure and a secondstructure is described made by a process comprising placing an adhesivewithin a bond cavity for bonding a first structure to a secondstructure, securing a vacuum bag to the first structure and the secondstructure so as to surround a portion of the first structure and thesecond structure, evacuating the bond cavity via a vacuum port todeaerate the adhesive within the evacuated bond cavity, after deaeratingthe adhesive, moving the first structure and the second structurerelative to one another such that deaerated adhesive is disposed betweenthe first structure and the second structure, and curing, via one ormore heaters, the deaerated adhesive disposed between the firststructure and the second structure to bond the first structure to thesecond structure and to form the bondline joining the first structureand the second structure.

In another example, a system for joining a first structure and a secondstructure is described. The system comprises one or more fixturesforming a bond cavity between a first structure and a second structurevia positioning of the first structure relative to the second structureand to cause movement of the first structure and the second structurerelative to one another, a vacuum bag to secure the first structure andthe second structure by surrounding a portion of the first structure andthe second structure, a vacuum port coupled to the vacuum bag forevacuating the bond cavity to deaerate an adhesive within the bondcavity such that deaerated adhesive is disposed between the firststructure and the second structure, and one or more heaters for curingthe deaerated adhesive disposed between the first structure and thesecond structure to bond the first structure to the second structure.

The features, functions, and advantages that have been discussed can beachieved independently in various examples or may be combined in yetother examples. Further details of the examples can be seen withreference to the following description and drawings.

BRIEF DESCRIPTION OF THE FIGURES

The novel features believed characteristic of the illustrative examplesare set forth in the appended claims. The illustrative examples,however, as well as a preferred mode of use, further objectives anddescriptions thereof, will best be understood by reference to thefollowing detailed description of an illustrative example of the presentdisclosure when read in conjunction with the accompanying drawings,wherein:

FIG. 1A illustrates a system for forming a bonded wing of an aircraft,according to an example implementation.

FIG. 1B illustrates an example of the aircraft including the bondedwing, according to an example implementation.

FIG. 2 illustrates the system with a portion of a wing skin coupled orbonded to the spars, the wing ribs, and the longerons, according to anexample implementation.

FIGS. 3A-3F illustrate an example process to join a first structure to asecond structure in a single-shear configuration, according to anexample implementation.

FIG. 4 illustrates an example of a system for joining the firststructure and the second structure, according to an exampleimplementation.

FIGS. 5A-5E illustrate another example process to join the firststructure to the second structure, according to an exampleimplementation.

FIGS. 6A-6G illustrate an example process to join the first structure tothe second structure in a dual-shear configuration, according to anexample implementation.

FIGS. 7A-7F illustrate another example process to join the firststructure to the second structure, according to an exampleimplementation.

FIG. 8 illustrates a flowchart of an example of a method of joining afirst structure and a second structure, according to an exampleimplementation.

FIG. 9 illustrates a flowchart of functions for use with the methodshown in FIG. 8 , according to an example implementation.

FIG. 10 illustrates a flowchart of functions for use with the methodshown in FIG. 8 , according to an example implementation.

FIG. 11 illustrates a flowchart of functions for use with the methodshown in FIG. 8 , according to an example implementation.

FIG. 12 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 13 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 14 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 15 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 16 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 17 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 18 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 19 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 20 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 21 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

FIG. 22 illustrates a flowchart of additional functions for use with themethod shown in FIG. 8 , according to an example implementation.

DETAILED DESCRIPTION

Disclosed examples will now be described more fully hereinafter withreference to the accompanying drawings, in which some, but not all ofthe disclosed examples are shown. Indeed, several different examples maybe described and should not be construed as limited to the examples setforth herein. Rather, these examples are described so that thisdisclosure will be thorough and complete and will fully convey the scopeof the disclosure to those skilled in the art.

Example systems and methods involve joining a first structure and asecond structure to create a void-free bondline between the firststructure and the second structure. An example method includes placingan adhesive within a bond cavity for bonding a first structure to asecond structure, securing a vacuum bag to the first structure and thesecond structure so as to surround a portion of the first structure andthe second structure, evacuating the bond cavity via a vacuum port todeaerate the adhesive within the bond cavity, after deaerating theadhesive, moving the first structure and the second structure relativeto one another such that deaerated adhesive is disposed between thefirst structure and the second structure, and curing, via one or moreheaters, the deaerated adhesive disposed between the first structure andthe second structure to bond the first structure to the secondstructure.

The example systems and methods can in some instances enable creatinghigh quality, void-free bondlines in bond configurations that aretraditionally high in void content, have high variation in strength, andwould otherwise take strength “knockdowns” in performance predictions.

In some examples described herein, collapsible stand-offs are used tomaintain gap fill widths for adhesive insertion between the firststructure and the second structure. The collapsible standoffs thencollapse at designated temperature and/or pressure combinations to forceout entrapped air that may otherwise create a void. Thus, thecollapsible stand-offs may control bondline thickness during a curingprocess and reduce gas entrapment to improve bondline quality.

FIG. 1A illustrates a system 100 for forming a bonded wing 102 of anaircraft 104, according to an example implementation. FIG. 1Billustrates an example of the aircraft 104 including the bonded wing102.

The system 100 includes a plurality of spars 106, which are held inplace by a plurality of fixture arms 108. The plurality of fixture arms108 are not included in the assembled wing, but are rather provided forpurposes of assembly. Other fixtures or tools can be used for holdingaspects of the system 100 in place during assembly. The system 100further includes a plurality of wing ribs 110, which are attachedbetween the spars 106. The system 100 further includes a plurality oflongerons 112, which run parallel to the spars 106, and which provide aninterface between the wing ribs 110 and other aspects of the system 100.The longerons 112 may provide a strength to the system 100.

The spars 106 can collectively form a portion of a wing box 114 thatprovides lateral structure to the system 100, and which provides ageneral shape and dimension of the system 100. Further, additionalcomponents of the system 100 may couple to the wing box 114.Accordingly, the dimensions of the spars 106 may strictly adhere todesign plans for the wing 102.

FIG. 2 illustrates the system 100 with a portion of a wing skin 116coupled or bonded to the spars 106, the wing ribs 110, and the longerons112, according to an example implementation. By coupling the wing skin116 to a component of the wing (e.g., the spars 106, the wing ribs 110,and the longerons 112), the bonded wing 102 is formed.

FIGS. 3A-3F, FIGS. 5A-5E, FIGS. 6A-6G, and FIGS. 7A-7F illustratevarious example phases of joining a first structure to a secondstructure, according example implementations. An example first structurecan include a component of the wing 102 of the aircraft 104, and anexample second structure can include the wing skin 116 of the wing 102of the aircraft 104. By joining the first structure and the secondstructure, a bondline is created between the first structure and thesecond structure. The first structure and the second structure caninclude other components of the wing 102 or other components of theaircraft 104 as well. For instance, in an example, the first structure120 and the second structure 122 can be a fuselage stringer and fuselageskin. Other examples are possible as well.

FIGS. 3A-3F illustrate an example process to join a first structure 120to a second structure 122 in a single-shear configuration, according toan example implementation. In particular, FIG. 3A shows across-sectional view of an initial stage of joining the first structure120 to the second structure 122. The first structure 120, which may be acomponent of a wing of an aircraft such as the spars 106, the wing ribs110, or the longerons 112, is held in placed with one or more fixtures(not shown in FIG. 3A, which can include the fixture arms 108 of FIG.1A) relative to the second structure 122, which can include or be thewing skin 116 of the wing of the aircraft.

As shown in FIG. 3A, the second structure 122 includes a base 126 and aflange 128 extending perpendicular to the base 126. The first structure120 is held in place by the fixture(s) (e.g., example fixtures shown inFIG. 4 ) so that the first structure 120 is adjacent to and parallelwith the flange 128. With the positioning of the first structure 120held in place adjacent to and parallel with the flange 128 of the secondstructure 122, a bond cavity 130 is formed between the first structure120 and the flange 128. Thus, the bond cavity 130 is formed between thefirst structure and the second structure 122 via positioning of thefirst structure 120 relative to the second structure 122.

Prior to positioning of the first structure 120 adjacent to and parallelwith the flange 128 of the second structure 122, adhesive 132 is placedon a surface 133 of the first structure 120 that faces the flange 128,and adhesive 132 is also placed on a surface 135 of the flange 128 thatfaces the first structure 120. The adhesive 132 can be a layer ofadhesive, as shown in FIG. 3A, that substantially covers surface area ofthe flange 128 and the first structure 120 over an area of each thatwill overlap when the flange 128 and the first structure 120 are broughttogether. For example, the adhesive 132 is shown to cover an entire (ora substantial portion) of the surface 135 of the flange 128 that facesthe first structure 120 whereas the adhesive 132 may only cover half ora bottom portion of the surface 133 of the first structure 120 thatfaces the flange 128.

In some examples, the adhesive 132 may only be placed on one of thefirst structure 120 or the flange 128. It is desired to place theadhesive 132 such that the adhesive 132 results within the bond cavity130 for bonding the first structure 120 to the second structure 122. Theadhesive 132 is also pre-placed on each bonding surface 133/135 of thefirst structure 120 and the second structure 122 prior to joining thefirst structure 120 and the second structure 122.

FIG. 3B illustrates a cross-sectional view of a subsequent stage inwhich a heater 134, such as a heat blanket, is positioned adjacent tothe bond cavity 130, by surrounding the flange 128 and the firststructure 120, for example. Following, perforated adhesive tape 136 isplaced at one or more exits 137 of the bond cavity 130 to allow vacuumthrough and to block flow of adhesive, for example. A semi-permeablebreather material 138 is then placed over the perforated adhesive tape136 at one or more exits 137 of the bond cavity 130. The semi-permeablebreather material 138 will assist to entrap the adhesive 132 whenjoining the first structure 120 to the second structure 122, forexample. The semi-permeable breather material 138 can include a materialsuch as foam or rubber, for example. The semi-permeable breathermaterial 138 can also include open cell foam, or semi-porous fiberglassmaterial, for example.

Then, a vacuum bag 140 is secured to the first structure 120 and thesecond structure 122 so as to surround a portion of the first structure120 and the second structure 122. Vacuum seal tape 142 is used to createa vacuum seal attachment of the vacuum bag 140 to the first structure120 and the second structure 122.

The vacuum bag 140 is applied to each side of the first structure 120and the second structure 122 to create a sealed enclosure. The vacuumbag 140 is placed around the heater 134 as well. The vacuum bag 140 caninclude a silicon rubber sheet or nylon film, for example.

In some examples, the heater 134 is optional, and a separate heatingelement is incorporated into the vacuum bag 140. Still other forms ofheating can be provided as well, such as forced air that convectivelyheats the adhesive or induction heating when inductable media is placedat or near the bond cavity 130.

In FIG. 3B, a vacuum port 144 is also coupled to the vacuum bag 140 forevacuating the bond cavity 130 via a vacuum (not shown).

FIG. 3C illustrates a cross-sectional view of a subsequent stage inwhich the bond cavity 130 is evacuated via the vacuum port 144 todeaerate the bond cavity 130 as well as to deaerate the adhesive 132within the bond cavity 130. Arrows are shown to illustrate air drawn outof the bond cavity 130 and out of the adhesive 132 and through theperforated adhesive tape 136 and the semi-permeable breather material138, and then out through the vacuum port 144. The semi-permeablebreather material 138 allows air to pass, but will prevent the adhesive132 from flowing out of the bond cavity 130. The air is evacuated fromall areas within the vacuum bag 140, for example, in order to evacuateall air out of areas where the adhesive 132 is placed to enable avoidfree bondline to be created between the first structure 120 and thesecond structure 122.

Further, by pre-placing the adhesive 132 on the first structure 120 andthe second structure 122, the adhesive 132 is de-aerated duringevacuation of the bond cavity 130 to further enable a voidfree bondlineto be created. De-aerated adhesive has no air, and thus, no voids ortrapped air bubbles will be present.

Note that the adhesive 132 illustrated in FIGS. 3A-3B includes airbubbles and has not yet been de-aerated. As seen by comparing FIGS. 3Bwith 3C, the evacuation of the bond cavity 130 removes air from theadhesive 132.

FIG. 3D illustrates a cross-sectional view of a subsequent stage inwhich after deaerating the adhesive 132, the first structure 120 and thesecond structure 122 are moved relative to one another such thatdeaerated adhesive is disposed between the first structure 120 and thesecond structure 122. To do so, the first structure 120 may be movedtoward the second structure 122, which can be stationary. Alternatively,the second structure 122 can be moved toward the first structure 120,which can be stationary. Still alternatively, both the first structure120 and the second structure 122 can be moved in a relative mannertoward one another.

FIG. 3D illustrates the first structure 120 and the second structure 122moved relative to one another so that each bonding surface 133/135 ofthe first structure 120 and the second structure 122 move toward eachother causing the deaerated adhesive 132 to be disposed in the bondcavity 130 between the first structure 120 and the second structure 122resulting in the deaerated adhesive 132 joining and bonding the firststructure 120 to the second structure 122. For example, fixtures (notshown in FIG. 3D) move the first structure 120 and the second structure122 relative to each other so that the deaerated adhesive 132 on each ofthe first structure 120 and the second structure 122 contacts and formsa bondline.

In the example shown in FIG. 3D, the bond cavity 130 is continuouslyevacuated via the vacuum port 144 while moving the first structure 120and the second structure 122 relative to one another. It may bebeneficial to continue evacuation via the vacuum port 144 to prevent anyair from seeping back into the bond cavity 130.

FIG. 3E illustrates a cross-sectional view of a subsequent stage inwhich the deaerated adhesive 132 disposed between the first structure120 and the second structure 122 is cured, via the heater 134, to bondthe first structure 120 to the second structure 122. In FIG. 3D, theheater 134 is activated causing heat 146 to flow through the firststructure 120, the flange 128 and to the deaerated adhesive 132. Theheater 134 can include a silicon rubber pad with resistive elements(e.g., flexible wires running through the pad) to provide resistanceheating, for example.

As shown in FIG. 3E, during curing of the deaerated adhesive 132, thevacuum continuously evacuates the bond cavity 130. In other examples,however, during curing of the deaerated adhesive 132, the vacuum can beshut off (manually or using an electronic valve).

FIG. 3F illustrates a cross-sectional view of a subsequent stage inwhich the heater 134 is turned off and components are removed from thefirst structure 120 and the second structure 122, and any excessadhesive is trimmed at edges resulting in a bondline 148 being formed tojoin the first structure 120 and the second structure 122. The bondline148 is a voidfree bondline, for example.

FIG. 4 illustrates an example of a system 150 for joining the firststructure 120 and the second structure 122, according to an exampleimplementation. The system 150 includes one or more fixtures 152 and 154forming the bond cavity 130 between the first structure 120 and thesecond structure 122 via positioning of the first structure 120 relativeto the second structure 122 and to cause movement of the first structure120 and the second structure 122 relative to one another. The system 150also includes the vacuum bag 140 to secure the first structure 120 andthe second structure 122 by surrounding a portion of the first structure120 and the second structure 122. The system 150 also includes thevacuum port 144 coupled to the vacuum bag 140 for evacuating the bondcavity 130 to deaerate the adhesive 132 within the bond cavity 130 suchthat deaerated adhesive is disposed between the first structure 120 andthe second structure 122. The system also includes one or more heaters(e.g., the heater 134) for curing the deaerated adhesive disposedbetween the first structure 120 and the second structure 122 to bond thefirst structure 120 to the second structure 122.

In FIG. 4 , the fixtures 152 and 154 are shown coupled to the firststructure 120 and the second structure 122 using a temporary adhesive151. The fixture 152 can include a slider rod 153 movable within atranslation sleeve 155 to enable movement of the first structure 120relative to the second structure 122, for example.

The system 150 in FIG. 4 can include more or fewer components as well,such as any of the additional components described in FIGS. 3A-3F, forexample.

FIGS. 5A-5E illustrate another example process to join the firststructure 120 to the second structure 122, according to an exampleimplementation. The processes illustrated in FIGS. 5A-5E are similar tothose illustrated in FIGS. 3A-3F, however, in the examples in FIGS.5A-5E, collapsible standoffs 156 and 158 are positioned between thefirst structure 120 and the second structure 122 to control a positionof the first structure 120 relative to the second structure 122.

As shown in FIG. 5A, the second structure 122 includes the base 126 andthe flange 128 extending perpendicular to the base 126. The firststructure 120 is held in place by the fixture(s) (e.g., example fixturesshown in FIG. 4 ) so that the first structure 120 is adjacent to andparallel with the flange 128. With the positioning of the firststructure 120 held in place adjacent to and parallel with the flange 128of the second structure 122, the bond cavity 130 is formed between thefirst structure 120 and the flange 128.

Prior to positioning of the first structure 120 adjacent to and parallelwith the flange 128 of the second structure 122, adhesive 132 is placedon a surface of the first structure 120 that faces the flange 128, andadhesive 132 is also placed on a surface of the flange 128 that facesthe first structure 120.

In addition, the collapsible standoffs 156 and 158 are used to control aposition of the first structure 120 relative to the second structure122, and are inserted between the first structure 120 and the secondstructure 122. In one example, the collapsible standoff 156 is placed ina hole 161 of a surface of the second structure 122, and the surface ofthe second structure 122 is configured to move toward the firststructure 120. Adhesive 132 can be placed in the hole 161 of the surfaceof the second structure 122 to bond the collapsible standoff 156 inplace. Similarly, the collapsible standoff 158 is placed in a hole 163of a surface of the first structure 120, and the surface of the firststructure 120 is configured to move toward the second structure 122.Adhesive 132 can be placed in the hole 163 of the surface of the firststructure 120 to bond the collapsible standoff 158 in place.

In other examples, the collapsible standoffs 156 and 158 are positionedin the adhesive 132 and remain in place on the first structure 120 andthe second structure 122.

Other components shown in FIG. 5A that are the same as shown in FIGS.3A-3F are not described again for simplicity and include the heater 134,the perforated adhesive tape 136, the semi-permeable breather material138, the vacuum bag 140, the vacuum seal tape 142, and the vacuum port144.

After positioning the components, the first structure 120 and the secondstructure 122 are moved relative to one another by forcing the firststructure 120 against the collapsible standoff 156 to contact thecollapsible standoff 156, and by forcing the second structure 122against the collapsible standoff 158 to contact the collapsible standoff158 and cause the adhesive to be positioned between the first structure120 and the second structure 122.

FIG. 5B illustrates a cross-sectional view of a subsequent stage inwhich the bond cavity 130 is evacuated via the vacuum port 144 todeaerate the bond cavity 130 as well as to deaerate the adhesive 132within the bond cavity 130. Arrows are shown to illustrate air drawn outof the bond cavity 130 and out of the adhesive 132 and through theperforated adhesive tape 136 and the semi-permeable breather material138, and then out through the vacuum port 144. The semi-permeablebreather material 138 allows air to pass, but will prevent the adhesive132 from flowing out of the bond cavity 130. The air is evacuated fromall areas within the vacuum bag 140, for example, in order to evacuateall air out of areas where the adhesive 132 is placed to enable avoidfree bondline to be created between the first structure 120 and thesecond structure 122.

Further, by pre-placing the adhesive 132 on the first structure 120 andthe second structure 122, the adhesive 132 is de-aerated duringevacuation of the bond cavity 130 to further enable a voidfree bondlineto be created. De-aerated adhesive has no air, and thus, no voids ortrapped air bubbles will be present.

FIG. 5C illustrates a cross-sectional view of a subsequent stage inwhich heat is applied by the heater 134. In FIG. 5C, the heater 134 isturned on causing heat to flow through the first structure 120, theflange 128 and the adhesive 132. The heater 134 can include a siliconrubber pad with resistive elements (e.g., flexible wires running throughthe pad) to provide resistance heating, for example.

When heating, the collapsible standoffs 156 and 158 collapse at apredetermined temperature due to thermal softening of the collapsiblestandoffs 156 and 158 to enable a bondline to form between the firststructure 120 and the second structure 122. The collapsible standoffs156 and 158 are structures designed with materials that soften undertemperature and pressure combinations, and can be fabricated usingadditive manufacturing, for example. For instance, the collapsiblestandoffs 156 and 158 may include thermoplastic material, materialsfabricated from fiber reinforced plastics, materials that may becompatible or may cross-link with the adhesive 132 of the bond,materials fabricated from adhesive that has or is modified to have ahigher melting temperature to thereby maintain a standoff or separationof the first structure 120 from the second structure 122 until athreshold temperature is reached.

Within examples, the collapsible standoffs 156 and 158 are a spiral orspring-like configuration, a truss configuration, a hollow columnconfiguration, or a wireframe-like configuration. In other examples, thecollapsible standoffs 156 and 158 include guide pin configurations toprovide component alignment and merging guidance, and the guide pins maybe pressed into pre-drilled holes in the first structure 120 and thesecond structure 122 with the collapsible standoffs 156 and 158positioned over the guide pins.

In still other examples, the collapsible standoffs 156 and 158 include asolenoid in a shoulder bolt to provide guide and controllablecollapsibility that is electrically or pneumatically actuated.

Within examples, the collapsible standoffs 156 and 158 collapse in aone-dimensional manner while providing alignment and spacing between thefirst structure 120 and the second structure 122.

FIG. 5D illustrates a cross-sectional view of a subsequent stage inwhich the heat is applied by the heater 134 and the collapsiblestandoffs 156 and 158 have been caused to collapse due to heating andthermal softening at a predetermined temperature. During this time, thebond cavity 130 can be continuously evacuated via the vacuum port 144drawing the first structure 120 and the second structure 122 toward eachother due to vacuum pressure, for example. The vacuum pressure alsoassists with causing the collapse of the collapsible standoffs 156 and158.

In some examples, heat is applied to achieve a first temperature tocause the collapsible standoffs 156 and 158 to collapse resulting in thefirst structure 120 and the second structure 122 moving toward eachother due to vacuum pressure, and then heat is applied to achieve asecond temperature higher than the first temperature to cure thedeaerated adhesive 132 and bond the first structure 120 to the secondstructure 122. In one example, the collapsible standoffs 156 and 158have a melting point of about 170° F. and the adhesive 132 has a curetemperature of about 350° F. Thus, the collapsible standoffs 156 and 158soften and collapse after reaching the first temperature of about 170°F., and then the heat is increased to the cure temperature to cure theadhesive 132.

FIG. 5E illustrates a cross-sectional view of a subsequent stage inwhich the heater 134 is turned off and components are removed from thefirst structure 120 and the second structure 122, and any excessadhesive is trimmed at edges resulting in a bondline 148 being formed tojoin the first structure 120 and the second structure 122. The bondline148 is a voidfree bondline, for example. A thickness of the bondline 148between the first structure 120 and the second structure 122 iscontrolled via a residual thickness of the collapsed collapsiblestandoffs 156 and 158.

FIGS. 6A-6G illustrate an example process to join the first structure120 to the second structure 122 in a dual-shear configuration, accordingto an example implementation. The processes illustrated in FIGS. 6A-6Gare similar to those illustrated in FIGS. 3A-3F, however, in theexamples in FIGS. 6A-6G, the second structure 122 has two flanges ratherthan one flange and the first structure 120 is positioned between thetwo flanges of the second structure 122.

As shown in FIG. 6A, the second structure 122 includes the base 126, theflange 128 extending perpendicular to the base 126, and the flange 160also extending perpendicular to the base 126. The first structure 120 isheld in place by the fixture(s) (e.g., example fixtures shown in FIG. 4) so that the first structure 120 can be positioned into the areabetween the flange 128 and the flange 160. With the positioning of thefirst structure 120 into the area between the flange 128 and the flange160, the bond cavity 130 is formed.

A spacer 162 is inserted into a bottom area of the bond cavity 130 toprohibit adhesive accumulation. For example, it is desirable to avoidthat overfilling the bond cavity with adhesive, and thus, the spacer 162is placed to prevent adhesive from filling the area. In one example, thespacer 162 includes a closed cell foam elastic member. The spacer 162also controls insertion depth of the first structure 120 relative to thesecond structure 122.

Prior to inserting the first structure 120 between the flange 128 andthe flange 160, the adhesive 132 is generally placed on a surface of thefirst structure 120 that will contact the flange 128 and the flange 160,and adhesive 132 is also placed on surfaces of the flange 128 and theflange 160.

FIG. 6B illustrates a cross-sectional view of a subsequent stage inwhich other components are applied including the heater 134, thesemi-permeable breather material 138, the vacuum bag 140, the vacuumseal tape 142, and the vacuum port 144. These components are the same asshown in FIGS. 3A-3F and are not described again for simplicity. Notethat in the example shown in FIG. 6B, the vacuum bag 140 has semi rigidand flexible portion to enable movement of the parts, and the exampleincludes two heaters (e.g., heaters 134) on each side of the secondstructure 122.

FIG. 6C illustrates a cross-sectional view of a subsequent stage inwhich after positioning the components, the bond cavity 130 is evacuatedvia the vacuum port 144 to deaerate the bond cavity 130 as well as todeaerate the adhesive 132 within the bond cavity 130.

FIG. 6D illustrates a cross-sectional view of a subsequent stage inwhich the first structure 120 is moved relative to the second structure122 after the adhesive 132 has been deaerated, so as to position thefirst structure 120 between the flange 128 and the flange 160. The bondcavity 130 continues to be evacuated during the movement. Arrows areshown to illustrate air drawn out of the bond cavity 130 and out of theadhesive 132 and through the semi-permeable breather material 138, andthen out through the vacuum port 144. Further, by pre-placing theadhesive 132 on the first structure 120 and the second structure 122,the adhesive 132 is de-aerated during evacuation of the bond cavity 130to further enable a voidfree bondline to be created. De-aerated adhesivehas no air, and thus, no voids or trapped air bubbles will be present.

After deaerating the adhesive 132, the first structure 120 and thesecond structure 122 are moved relative to one another such thatdeaerated adhesive is disposed between the first structure 120 and thesecond structure 122. To do so, the first structure 120 may be movedtoward the second structure 122, which can be stationary. Alternatively,the second structure 122 can be moved toward the first structure 120,which can be stationary. Still alternatively, both the first structure120 and the second structure 122 can be moved in a relative mannertoward one another.

FIG. 6E illustrates a cross-sectional view of a subsequent stage inwhich the first structure 120 is further moved relative to the secondstructure 122 so as to position the first structure 120 between theflange 128 and the flange 160, and to contact the spacer 162 at a bottomof the bond cavity 130. In the example shown in FIG. 6E, the bond cavity130 is continuously evacuated via the vacuum port 144 while moving thefirst structure 120 and the second structure 122 relative to oneanother. It may be beneficial to continue evacuation via the vacuum port144 to prevent any air from seeping back into the bond cavity 130.

FIG. 6F illustrates a cross-sectional view of a subsequent stage inwhich the deaerated adhesive 132 disposed between the first structure120 and the second structure 122 is cured, via the heater 134, to bondthe first structure 120 to the second structure 122. In FIG. 6F, theheater 134 is turned on causing heat to flow through the first structure120, the flange 128, the flange 160, and the adhesive 132. The heater134 can include a silicon rubber pad with resistive elements (e.g.,flexible wires running through the pad) to provide resistance heating,for example.

As shown in FIG. 6F, during curing of the adhesive 132, the vacuumcontinuously evacuates the bond cavity 130. In other examples, however,during curing of the adhesive 132, the vacuum can be shut off (manuallyor using an electronic valve).

FIG. 6G illustrates a cross-sectional view of a subsequent stage inwhich the heater 134 is turned off and components are removed from thefirst structure 120 and the second structure 122, and any excessadhesive is trimmed at edges resulting in a bondline 148 being formed tojoin the first structure 120 and the second structure 122. The bondline148 is a voidfree bondline, for example.

FIGS. 7A-7F illustrate another example process to join the firststructure 120 to the second structure 122, according to an exampleimplementation. The processes illustrated in FIGS. 7A-7F are similar tothose illustrated in FIGS. 6A-6G, however, in the examples in FIGS.7A-7E, a collapsible standoff 164 is positioned at a bottom of the bondcavity 130.

As shown in FIG. 7A, the second structure 122 includes the base 126, theflange 128 extending perpendicular to the base 126, and the flange 160also extending perpendicular to the base 126. The first structure 120 isheld in place by the fixture(s) (e.g., example fixtures shown in FIG. 4) so that the first structure 120 can be positioned into the areabetween the flange 128 and the flange 160. With the positioning of thefirst structure 120 into the area between the flange 128 and the flange160, the bond cavity 130 is formed.

The collapsible standoff 164 is inserted into a bottom area of the bondcavity 130 to control bondline thickness. The collapsible standoff 164also controls a distance that the first structure 120 extends into thebond cavity 130 based on temperature. For example, the collapsiblestandoff 164 will collapse once heated to a threshold temperatureallowing compression of the collapsible standoff 164.

An amount of adhesive 166 is then inserted into the bond cavity 130 ontop of the collapsible standoff 164. The adhesive 166 of FIG. 7A is notde-aerated.

FIG. 7B illustrates a cross-sectional view of a subsequent stage inwhich other components are applied including the heater 134, thesemi-permeable breather material 138, the vacuum bag 140, the vacuumseal tape 142, and the vacuum port 144. These components are the same asshown in FIGS. 6A-6E and are not described again for simplicity.

After positioning the components, the bond cavity 130 is evacuated viathe vacuum port 144 to deaerate the bond cavity 130 as well as todeaerate the adhesive 166 within the bond cavity 130. As can be seen bycomparing FIGS. 7A with 7B, evacuation of the bond cavity 130 removesair from the adhesive 166.

FIG. 7C illustrates a cross-sectional view of a subsequent stage inwhich the first structure 120 is moved relative to the second structure122 so as to position the first structure 120 between the flange 128 andthe flange 160. The bond cavity 130 continues to be evacuated during themovement. Arrows are shown to illustrate air drawn out of the bondcavity 130 and out of the adhesive 166 and through the semi-permeablebreather material 138, and then out through the vacuum port 144.Further, by pre-placing the adhesive 166 in the bond cavity 130, theadhesive 166 is de-aerated during evacuation of the bond cavity 130 tofurther enable a voidfree bondline to be created. De-aerated adhesivehas no air, and thus, no voids or trapped air bubbles will be present.

By moving the first structure 120 into the bond cavity 130, the firststructure 120 contacts the adhesive 166 causing the adhesive to surroundthe first structure 120, for example. Further movement of the firststructure 120 into the bond cavity 130 causes the adhesive 166 to fillthe bond cavity. In addition, capillarity will induce a uniform fill ofthe bond cavity 130 with the adhesive 166, for example.

FIG. 7E illustrates a cross-sectional view of a subsequent stage inwhich the deaerated adhesive 166 disposed between the first structure120 and the second structure 122 is cured, via the heater 134, to bondthe first structure 120 to the second structure 122. The adhesive 166 isillustrated as filling the bond cavity 130, as mentioned, due tocapillarity and movement of the first structure 120. In FIG. 7E, theheater 134 is turned on causing heat to flow through the first structure120, the flange 128, the flange 160, and the adhesive 166. The heater134 can include a silicon rubber pad with resistive elements (e.g.,flexible wires running through the pad) to provide resistance heating,for example.

As shown in FIG. 7E, during curing of the adhesive 166, the vacuumcontinuously evacuates the bond cavity 130. In other examples, however,during curing of the adhesive 166, the vacuum can be shut off (manuallyor using an electronic valve).

When heating, the collapsible standoff 164 collapses at a predeterminedtemperature due to thermal softening of the collapsible standoff 164 toenable a bondline to form between the first structure 120 and the secondstructure 122. The collapsible standoff 164 may be the same as orfabricated use the same materials as the collapsible standoffs 156 and158, for example.

FIG. 7F illustrates a cross-sectional view of a subsequent stage inwhich the heater 134 is turned off and components are removed from thefirst structure 120 and the second structure 122, and any excessadhesive is trimmed at edges resulting in a bondline 148 being formed tojoin the first structure 120 and the second structure 122. The bondline148 is a voidfree bondline, for example. A thickness of the bondline 148between the first structure 120 and the second structure 122 iscontrolled via a residual thickness of the collapsed collapsiblestandoff 164.

FIG. 8 illustrates a flowchart of an example of a method 200 of joininga first structure 120 and a second structure 122, according to anexample implementation. Method 200 shown in FIG. 8 presents an exampleof a method that could be used with the system 150 or with components ofthereof. Further, the functions described with respect to FIG. 8 may besupplemented by, replaced by, or combined with functions and phasesdescribed above with respect to FIGS. 3A-3F, FIG. 4 , FIGS. 5A-5E, FIGS.6A-6G, and FIGS. 7A-7F, for example. Further, devices or systems may beused or configured to perform logical functions presented in FIG. 8 .

In one example, the method 200, and any of the phases shown in FIGS. 3-7, is considered a choreographed adhesive de-aeration process in whichstages of the process when performed in order provide a de-aeratedadhesive useful to join the first structure 120 and the second structure122 to form a bondline.

In some instances, components of the devices and/or systems may beconfigured to perform the functions such that the components areactually configured and structured (with hardware and/or software) toenable such performance. In other examples, components of the devicesand/or systems may be arranged to be adapted to, capable of, or suitedfor performing the functions, such as when operated in a specificmanner. Method 200 includes one or more operations, functions, oractions as illustrated by one or more of blocks 202-210. Further, blocksof FIGS. 9-22 may be performed in accordance with one or more of blocks202-210. Although the blocks are illustrated in a sequential order,these blocks may also be performed in parallel, and/or in a differentorder than those described herein. Also, the various blocks may becombined into fewer blocks, divided into additional blocks, and/orremoved based upon the desired implementation.

Within examples, one or more blocks of the method 200 may be representedin program code or circuitry used for controlling robotic mechanisms forjoining the first structure and the second structure (e.g., as forassembling a bonded structure and/or a wing including a plurality ofbonded structures). While method 200 and variations thereof may beexecuted automatically using, for example, one or more robotic armaturescontrolled by program code operating in accordance with the method 200,some tasks may be performed manually. Thus, within examples, certainfunctionality described with respect to the method 200 may be performedautomatically while other portions can be performed manually.Alternatively, all blocks of the method 200 may be performedautomatically or all blocks of the method 200 may be performed manually.

At block 202, the method 200 includes placing the adhesive 132 withinthe bond cavity 130 for bonding the first structure 120 to the secondstructure 122.

FIG. 9 illustrates a flowchart of functions for use with the method 200shown in FIG. 8 , according to an example implementation. In particular,FIG. 9 illustrates block 212, which includes an example function forplacing the adhesive 132 within the bond cavity 130 for bonding thefirst structure 120 to the second structure 122 including pre-placingthe adhesive 132 on each bonding surface of the first structure 120 andthe second structure 122.

FIG. 10 illustrates a flowchart of functions for use with the method 200shown in FIG. 8 , according to an example implementation. In particular,FIG. 10 illustrates block 214, which includes an example function forplacing the adhesive 132 within the bond cavity 130 for bonding thefirst structure 120 to the second structure 122 including placing theadhesive 132 within the bond cavity 130 for bonding a component of awing of an aircraft and a wing skin of the wing of the aircraft.

Referring back to FIG. 8 , at block 204, the method 200 includessecuring the vacuum bag 140 to the first structure 120 and the secondstructure 122 so as to surround a portion of the first structure 120 andthe second structure 122.

At block 206, the method 200 includes evacuating the bond cavity 130 viathe vacuum port 144 to deaerate the adhesive 132 within the bond cavity130.

At block 208, the method 200 includes after deaerating the adhesive 132,moving the first structure 120 and the second structure 122 relative toone another such that deaerated adhesive is disposed between the firststructure 120 and the second structure 122.

FIG. 11 illustrates a flowchart of functions for use with the method 200shown in FIG. 8 , according to an example implementation. In particular,FIG. 11 illustrates block 216, which includes an example function formoving the first structure 120 and the second structure 122 relative toone another including moving the first structure 120 and the secondstructure 122 so that each bonding surface of the first structure 120and the second structure 122 move toward each other.

Referring back to FIG. 8 , at block 210, the method 200 includes curing,via one or more heaters 134, the deaerated adhesive disposed between thefirst structure 120 and the second structure 122 to bond the firststructure 120 to the second structure 122.

FIG. 12 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 12 illustrates block 218, which includes an examplefunction for forming the bond cavity 130 between the first structure 120and the second structure 122 via positioning of the first structure 120relative to the second structure 122.

FIG. 13 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 13 illustrates block 220, which includes an examplefunction for moving the first structure 120 and the second structure 122relative to one another causing the deaerated adhesive to be disposed inthe bond cavity 130 between the first structure 120 and the secondstructure 122.

FIG. 14 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 14 illustrates block 222, which includes an examplefunction for inserting a spacer 162 into a bottom area of the bondcavity 130 to control bondline thickness.

FIG. 15 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 15 illustrates block 224, which includes an examplefunction for inserting a collapsible standoff 164 into a bottom area ofthe bond cavity 130 to control a distance of distribution of theadhesive 132 into the bond cavity 130 based on temperature, and thecollapsible standoff 164 collapses at a predetermined temperature.

FIG. 16 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 16 illustrates block 226, which includes an examplefunction for placing the semi-permeable breather material 138 at the oneor more exits 137 of the bond cavity 130.

FIG. 17 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 17 illustrates block 228, which includes an examplefunction for continuously evacuating the bond cavity 130 via the vacuumport 144 while moving the first structure 120 and the second structure122 relative to one another.

FIG. 18 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 18 illustrates block 230, which includes an examplefunction for controlling a position of the first structure 120 relativeto the second structure 122 via a collapsible standoff 156/158/164, andthe collapsible standoff 156/158/164 collapses at a predeterminedtemperature due to thermal softening of the collapsible standoff156/158/164.

FIG. 19 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 19 illustrates block 232, which includes an examplefunction for controlling a thickness of a bondline between the firststructure 120 and the second structure 122 via a residual thickness of acollapsed collapsible standoff 156/158/164.

FIG. 20 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 20 illustrates blocks 234, 236, and 238. At block 234,an example function includes placing a collapsible standoff 156 in ahole 161 of a surface of the second structure 122, and the surface ofthe second structure 122 is configured to move toward the firststructure 120. At block 236, an example function includes placing theadhesive 132 in the hole 161 of the surface of the second structure 122.At block 238, an example function includes forcing the first structure120 against the collapsible standoff 156 to contact the collapsiblestandoff 156 and force the adhesive 132 to flow between the firststructure 120 and the second structure 122.

FIG. 21 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 21 illustrates blocks 240 and 242. At block 240, anexample function includes while curing the deaerated adhesive disposedbetween the first structure 120 and the second structure 122 to bond thefirst structure 120 to the second structure 122, causing the collapsiblestandoff 156 to collapse due to heating and thermal softening at apredetermined temperature, and at block 242 an example function includescontinuously evacuating the bond cavity via the vacuum port 144 drawingthe first structure 120 and the second structure 122 toward each other.

FIG. 22 illustrates a flowchart of additional functions for use with themethod 200 shown in FIG. 8 , according to an example implementation. Inparticular, FIG. 22 illustrates blocks 244, 246, and 248. At block 244,an example function includes placing a collapsible standoff 156/158between the first structure 120 and the second structure 122 to controla position of the first structure 120 relative to the second structure122, and the collapsible standoff 156/158 collapses at a predeterminedtemperature due to thermal softening. At block 246, an example functionincludes applying heat to achieve a first temperature to cause thecollapsible standoff 156/158 to collapse resulting in the firststructure 120 and the second structure 122 moving toward each other dueto vacuum pressure. At block 248, an example function includes applyingheat to achieve a second temperature higher than the first temperatureto cure the deaerated adhesive and bond the first structure 120 to thesecond structure 122.

Using example methods and systems described herein can enable creationof bonded structures that have improved strength and higher quality. Forinstance, the example methods and systems described herein can enablecreation of voidfree bondlines in pi joints and single shear joints inaircraft. This results from adhesive being de-aerated within the bondcavity so that no or reduced voids are included in the resultingbondline.

By the term “substantially,” “similarity,” and “about” used herein, itis meant that the recited characteristic, parameter, or value need notbe achieved exactly, but that deviations or variations, including forexample, tolerances, measurement error, measurement accuracy limitationsand other factors known to skill in the art, may occur in amounts thatdo not preclude the effect the characteristic was intended to provide.

Different examples of the system(s), device(s), and method(s) disclosedherein include a variety of components, features, and functionalities.It should be understood that the various examples of the system(s),device(s), and method(s) disclosed herein may include any of thecomponents, features, and functionalities of any of the other examplesof the system(s), device(s), and method(s) disclosed herein in anycombination or any sub-combination, and all of such possibilities areintended to be within the scope of the disclosure.

The description of the different advantageous arrangements has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the examples in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different advantageous examplesmay describe different advantages as compared to other advantageousexamples. The example or examples selected are chosen and described inorder to best explain the principles of the examples, the practicalapplication, and to enable others of ordinary skill in the art tounderstand the disclosure for various examples with variousmodifications as are suited to the particular use contemplated.

What is claimed is:
 1. A system for joining a first structure and asecond structure, the system comprising: one or more fixtures forming abond cavity between a first structure and a second structure viapositioning of the first structure relative to the second structure andto cause movement of the first structure and the second structurerelative to one another; a vacuum bag to secure the first structure andthe second structure by surrounding a portion of the first structure andthe second structure; a vacuum port coupled to the vacuum bag forevacuating the bond cavity to deaerate an adhesive within the bondcavity such that deaerated adhesive is disposed between the firststructure and the second structure; and one or more heaters for curingthe deaerated adhesive disposed between the first structure and thesecond structure to bond the first structure to the second structure. 2.The system of claim 1, further comprising: a collapsible standoffpositioned between the first structure and the second structure tocontrol a position of the first structure relative to the secondstructure, wherein the collapsible standoff collapses at a predeterminedtemperature.
 3. The system of claim 1, further comprising: a collapsiblestandoff positioned in the adhesive within the bond cavity.
 4. Thesystem of claim 1, wherein the adhesive is placed within the bond cavityon each bonding surface of the first structure and the second structurefor bonding the first structure to the second structure.
 5. The systemof claim 1, further comprising: a spacer inserted into a bottom area ofthe bond cavity to control bondline thickness.
 6. The system of claim 1,further comprising: a collapsible standoff inserted into a bottom areaof the bond cavity to control a distance of distribution of the adhesiveinto the bond cavity based on temperature, wherein the collapsiblestandoff collapses at a predetermined temperature.
 7. The system ofclaim 6, wherein a thickness of a bondline between the first structureand the second structure is controlled via a residual thickness of acollapsed collapsible standoff.
 8. The system of claim 1, furthercomprising: a semi-permeable breather material placed at one or moreexits of the bond cavity.
 9. The system of claim 1, wherein the vacuumport continuously evacuates the bond cavity while the one or morefixtures cause movement of the first structure and the second structureto one another.
 10. The system of claim 1, further comprising: acollapsible standoff placed in a hole of a surface of the secondstructure, wherein the surface of the second structure is configured tomove toward the first structure, wherein the adhesive is placed in thehole of the surface of the second structure, and wherein the one or morefixtures cause movement of the first structure and the second structurerelative to one another to force the first structure against thecollapsible standoff to contact the collapsible standoff and force theadhesive to flow between the first structure and the second structure.11. The system of claim 10, wherein the one or more heaters cure thedeaerated adhesive and cause the collapsible standoff to collapse due toheating and thermal softening at a predetermined temperature.
 12. Thesystem of claim 11, wherein the vacuum port continuously evacuates thebond cavity while the one or more heaters cure the deaerated adhesive.13. The system of claim 1, further comprising: a collapsible standoffplaced between the first structure and the second structure to control aposition of the first structure relative to the second structure,wherein the collapsible standoff collapses at a predeterminedtemperature due to thermal softening; the one or more heaters apply heatto achieve a first temperature to cause the collapsible standoff tocollapse resulting in the first structure and the second structuremoving toward each other due to vacuum pressure.
 14. The system of claim13, wherein the one or more heaters apply heat to achieve a secondtemperature higher than the first temperature to cure the deaeratedadhesive and bond the first structure to the second structure.
 15. Thesystem of claim 1, wherein the first structure comprises a component ofa wing of an aircraft and the second structure comprises a wing skin ofthe wing of the aircraft.
 16. A system for joining a first structure anda second structure, the system comprising: one or more fixtures forminga bond cavity between a first structure and a second structure viapositioning of the first structure relative to the second structure andto cause movement of the first structure and the second structurerelative to one another; a collapsible standoff positioned between thefirst structure and the second structure to control a position of thefirst structure relative to the second structure; a vacuum bag to securethe first structure and the second structure by surrounding a portion ofthe first structure and the second structure; a vacuum port coupled tothe vacuum bag for evacuating the bond cavity to deaerate an adhesivewithin the bond cavity such that deaerated adhesive is disposed betweenthe first structure and the second structure; and one or more heatersfor curing the deaerated adhesive disposed between the first structureand the second structure to bond the first structure to the secondstructure.
 17. The system of claim 16, wherein the collapsible standoffcomprises include a thermoplastic material.
 18. The system of claim 16,wherein the collapsible standoff comprises a spiral or spring-likeconfiguration.
 19. The system of claim 16, wherein the collapsiblestandoff comprises a hollow column configuration.
 20. The system ofclaim 16, wherein the collapsible standoff collapses in aone-dimensional manner while providing alignment and spacing between thefirst structure and the second structure.